![Eryu Guan](/assets/img/avatar_default.png)
Since commit d531d91d69
("xfs: always use unwritten extents for
direct I/O writes"), we start allocating unwritten extents for all
direct writes to allow appending aio in XFS.
But for dio writes that could extend file size we update the in-core
inode size first, then convert the unwritten extents to real
allocations at dio completion time in xfs_dio_write_end_io(). Thus a
racing direct read could see the new i_size and find the unwritten
extents first and read zeros instead of actual data, if the direct
writer also takes a shared iolock.
Fix it by updating the in-core inode size after the unwritten extent
conversion. To do this, introduce a new boolean argument to
xfs_iomap_write_unwritten() to tell if we want to update in-core
i_size or not.
Suggested-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Eryu Guan <eguan@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
309 lines
7.4 KiB
C
309 lines
7.4 KiB
C
/*
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* Copyright (c) 2014 Christoph Hellwig.
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*/
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#include <linux/iomap.h>
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#include "xfs.h"
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#include "xfs_format.h"
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#include "xfs_log_format.h"
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#include "xfs_trans_resv.h"
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#include "xfs_sb.h"
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#include "xfs_mount.h"
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#include "xfs_inode.h"
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#include "xfs_trans.h"
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#include "xfs_log.h"
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#include "xfs_bmap.h"
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#include "xfs_bmap_util.h"
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#include "xfs_error.h"
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#include "xfs_iomap.h"
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#include "xfs_shared.h"
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#include "xfs_bit.h"
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#include "xfs_pnfs.h"
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/*
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* Ensure that we do not have any outstanding pNFS layouts that can be used by
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* clients to directly read from or write to this inode. This must be called
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* before every operation that can remove blocks from the extent map.
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* Additionally we call it during the write operation, where aren't concerned
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* about exposing unallocated blocks but just want to provide basic
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* synchronization between a local writer and pNFS clients. mmap writes would
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* also benefit from this sort of synchronization, but due to the tricky locking
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* rules in the page fault path we don't bother.
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*/
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int
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xfs_break_layouts(
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struct inode *inode,
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uint *iolock)
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{
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struct xfs_inode *ip = XFS_I(inode);
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int error;
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ASSERT(xfs_isilocked(ip, XFS_IOLOCK_SHARED|XFS_IOLOCK_EXCL));
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while ((error = break_layout(inode, false) == -EWOULDBLOCK)) {
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xfs_iunlock(ip, *iolock);
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error = break_layout(inode, true);
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*iolock = XFS_IOLOCK_EXCL;
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xfs_ilock(ip, *iolock);
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}
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return error;
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}
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/*
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* Get a unique ID including its location so that the client can identify
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* the exported device.
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*/
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int
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xfs_fs_get_uuid(
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struct super_block *sb,
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u8 *buf,
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u32 *len,
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u64 *offset)
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{
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struct xfs_mount *mp = XFS_M(sb);
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printk_once(KERN_NOTICE
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"XFS (%s): using experimental pNFS feature, use at your own risk!\n",
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mp->m_fsname);
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if (*len < sizeof(uuid_t))
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return -EINVAL;
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memcpy(buf, &mp->m_sb.sb_uuid, sizeof(uuid_t));
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*len = sizeof(uuid_t);
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*offset = offsetof(struct xfs_dsb, sb_uuid);
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return 0;
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}
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/*
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* Get a layout for the pNFS client.
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*/
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int
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xfs_fs_map_blocks(
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struct inode *inode,
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loff_t offset,
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u64 length,
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struct iomap *iomap,
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bool write,
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u32 *device_generation)
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{
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struct xfs_inode *ip = XFS_I(inode);
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struct xfs_mount *mp = ip->i_mount;
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struct xfs_bmbt_irec imap;
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xfs_fileoff_t offset_fsb, end_fsb;
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loff_t limit;
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int bmapi_flags = XFS_BMAPI_ENTIRE;
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int nimaps = 1;
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uint lock_flags;
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int error = 0;
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if (XFS_FORCED_SHUTDOWN(mp))
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return -EIO;
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/*
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* We can't export inodes residing on the realtime device. The realtime
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* device doesn't have a UUID to identify it, so the client has no way
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* to find it.
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*/
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if (XFS_IS_REALTIME_INODE(ip))
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return -ENXIO;
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/*
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* The pNFS block layout spec actually supports reflink like
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* functionality, but the Linux pNFS server doesn't implement it yet.
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*/
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if (xfs_is_reflink_inode(ip))
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return -ENXIO;
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/*
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* Lock out any other I/O before we flush and invalidate the pagecache,
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* and then hand out a layout to the remote system. This is very
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* similar to direct I/O, except that the synchronization is much more
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* complicated. See the comment near xfs_break_layouts for a detailed
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* explanation.
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*/
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xfs_ilock(ip, XFS_IOLOCK_EXCL);
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error = -EINVAL;
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limit = mp->m_super->s_maxbytes;
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if (!write)
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limit = max(limit, round_up(i_size_read(inode),
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inode->i_sb->s_blocksize));
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if (offset > limit)
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goto out_unlock;
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if (offset > limit - length)
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length = limit - offset;
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error = filemap_write_and_wait(inode->i_mapping);
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if (error)
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goto out_unlock;
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error = invalidate_inode_pages2(inode->i_mapping);
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if (WARN_ON_ONCE(error))
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return error;
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end_fsb = XFS_B_TO_FSB(mp, (xfs_ufsize_t)offset + length);
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offset_fsb = XFS_B_TO_FSBT(mp, offset);
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lock_flags = xfs_ilock_data_map_shared(ip);
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error = xfs_bmapi_read(ip, offset_fsb, end_fsb - offset_fsb,
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&imap, &nimaps, bmapi_flags);
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xfs_iunlock(ip, lock_flags);
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if (error)
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goto out_unlock;
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if (write) {
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enum xfs_prealloc_flags flags = 0;
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ASSERT(imap.br_startblock != DELAYSTARTBLOCK);
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if (!nimaps || imap.br_startblock == HOLESTARTBLOCK) {
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/*
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* xfs_iomap_write_direct() expects to take ownership of
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* the shared ilock.
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*/
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xfs_ilock(ip, XFS_ILOCK_SHARED);
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error = xfs_iomap_write_direct(ip, offset, length,
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&imap, nimaps);
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if (error)
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goto out_unlock;
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/*
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* Ensure the next transaction is committed
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* synchronously so that the blocks allocated and
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* handed out to the client are guaranteed to be
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* present even after a server crash.
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*/
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flags |= XFS_PREALLOC_SET | XFS_PREALLOC_SYNC;
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}
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error = xfs_update_prealloc_flags(ip, flags);
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if (error)
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goto out_unlock;
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}
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xfs_iunlock(ip, XFS_IOLOCK_EXCL);
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xfs_bmbt_to_iomap(ip, iomap, &imap);
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*device_generation = mp->m_generation;
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return error;
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out_unlock:
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xfs_iunlock(ip, XFS_IOLOCK_EXCL);
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return error;
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}
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/*
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* Ensure the size update falls into a valid allocated block.
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*/
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static int
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xfs_pnfs_validate_isize(
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struct xfs_inode *ip,
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xfs_off_t isize)
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{
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struct xfs_bmbt_irec imap;
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int nimaps = 1;
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int error = 0;
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xfs_ilock(ip, XFS_ILOCK_SHARED);
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error = xfs_bmapi_read(ip, XFS_B_TO_FSBT(ip->i_mount, isize - 1), 1,
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&imap, &nimaps, 0);
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xfs_iunlock(ip, XFS_ILOCK_SHARED);
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if (error)
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return error;
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if (imap.br_startblock == HOLESTARTBLOCK ||
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imap.br_startblock == DELAYSTARTBLOCK ||
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imap.br_state == XFS_EXT_UNWRITTEN)
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return -EIO;
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return 0;
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}
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/*
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* Make sure the blocks described by maps are stable on disk. This includes
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* converting any unwritten extents, flushing the disk cache and updating the
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* time stamps.
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*
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* Note that we rely on the caller to always send us a timestamp update so that
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* we always commit a transaction here. If that stops being true we will have
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* to manually flush the cache here similar to what the fsync code path does
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* for datasyncs on files that have no dirty metadata.
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*/
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int
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xfs_fs_commit_blocks(
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struct inode *inode,
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struct iomap *maps,
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int nr_maps,
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struct iattr *iattr)
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{
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struct xfs_inode *ip = XFS_I(inode);
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struct xfs_mount *mp = ip->i_mount;
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struct xfs_trans *tp;
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bool update_isize = false;
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int error, i;
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loff_t size;
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ASSERT(iattr->ia_valid & (ATTR_ATIME|ATTR_CTIME|ATTR_MTIME));
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xfs_ilock(ip, XFS_IOLOCK_EXCL);
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size = i_size_read(inode);
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if ((iattr->ia_valid & ATTR_SIZE) && iattr->ia_size > size) {
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update_isize = true;
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size = iattr->ia_size;
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}
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for (i = 0; i < nr_maps; i++) {
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u64 start, length, end;
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start = maps[i].offset;
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if (start > size)
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continue;
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end = start + maps[i].length;
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if (end > size)
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end = size;
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length = end - start;
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if (!length)
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continue;
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/*
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* Make sure reads through the pagecache see the new data.
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*/
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error = invalidate_inode_pages2_range(inode->i_mapping,
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start >> PAGE_SHIFT,
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(end - 1) >> PAGE_SHIFT);
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WARN_ON_ONCE(error);
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error = xfs_iomap_write_unwritten(ip, start, length, false);
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if (error)
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goto out_drop_iolock;
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}
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if (update_isize) {
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error = xfs_pnfs_validate_isize(ip, size);
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if (error)
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goto out_drop_iolock;
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}
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error = xfs_trans_alloc(mp, &M_RES(mp)->tr_ichange, 0, 0, 0, &tp);
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if (error)
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goto out_drop_iolock;
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xfs_ilock(ip, XFS_ILOCK_EXCL);
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xfs_trans_ijoin(tp, ip, XFS_ILOCK_EXCL);
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xfs_trans_log_inode(tp, ip, XFS_ILOG_CORE);
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xfs_setattr_time(ip, iattr);
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if (update_isize) {
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i_size_write(inode, iattr->ia_size);
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ip->i_d.di_size = iattr->ia_size;
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}
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xfs_trans_set_sync(tp);
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error = xfs_trans_commit(tp);
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out_drop_iolock:
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xfs_iunlock(ip, XFS_IOLOCK_EXCL);
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return error;
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}
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